Why is glass material increasing noise, and what to do about it?
Short version: glass shader is more complicated and needs more calculations to obtain a nice result. So either you set samples to higher values, either you use some trickeries in the shader or in the rendering settings in order to reduce the complexity (but at the cost of accuracy).

I invite you to read the Blender Manual about Glass BSDF, which explains this more precisely as well as giving you ways to reduce noise.